Skip dangling images (#98)

internal/provider/docker/container.go

@@ -36,14 +36,20 @@ func (c *Client) listContainerImage() []model.Image {
 
 	var list []model.Image
 	for _, ctn := range ctns {
-		local, err := cli.IsLocalImage(ctn.Image)
+		imageRaw, err := cli.RawImage(ctn.Image)
 		if err != nil {
 			c.logger.Error().Err(err).Msgf("Cannot inspect image from container %s", ctn.ID)
 			continue
-		} else if local {
-			c.logger.Debug().Msgf("Skip locally built image for container %s", ctn.ID)
+		}
+		if local := cli.IsLocalImage(imageRaw); local {
+			c.logger.Debug().Msgf("Skip locally built image from container %s", ctn.ID)
 			continue
 		}
+		if dangling := cli.IsDanglingImage(imageRaw); dangling {
+			c.logger.Debug().Msgf("Skip dangling image from container %s", ctn.ID)
+			continue
+		}
+
 		image, err := provider.ValidateContainerImage(ctn.Image, ctn.Labels, *c.config.WatchByDefault)
 		if err != nil {
 			c.logger.Error().Err(err).Msgf("Cannot get image from container %s", ctn.ID)

internal/provider/swarm/service.go

@@ -29,11 +29,17 @@ func (c *Client) listServiceImage() []model.Image {
 
 	var list []model.Image
 	for _, svc := range svcs {
-		local, _ := cli.IsLocalImage(svc.Spec.TaskTemplate.ContainerSpec.Image)
-		if local {
-			c.logger.Debug().Msgf("Skip locally built image for service %s", svc.Spec.Name)
-			continue
+		if imageRaw, err := cli.RawImage(svc.Spec.TaskTemplate.ContainerSpec.Image); err == nil {
+			if local := cli.IsLocalImage(imageRaw); local {
+				c.logger.Debug().Msgf("Skip locally built image for service %s", svc.Spec.Name)
+				continue
+			}
+			if dangling := cli.IsDanglingImage(imageRaw); dangling {
+				c.logger.Debug().Msgf("Skip dangling image for service %s", svc.Spec.Name)
+				continue
+			}
 		}
+
 		image, err := provider.ValidateContainerImage(svc.Spec.TaskTemplate.ContainerSpec.Image, svc.Spec.Labels, *c.config.WatchByDefault)
 		if err != nil {
 			c.logger.Error().Err(err).Msgf("Cannot get image from service %s", svc.Spec.Name)

pkg/docker/image.go

@@ -1,10 +1,21 @@
 package docker
 
-// IsLocalImage checks if the image has been built locally
-func (c *Client) IsLocalImage(image string) (bool, error) {
-	raw, _, err := c.API.ImageInspectWithRaw(c.ctx, image)
-	if err != nil {
-		return false, err
-	}
-	return len(raw.RepoDigests) == 0, nil
+import "github.com/docker/docker/api/types"
+
+// RawImage returns the image information and its raw representation
+func (c *Client) RawImage(image string) (types.ImageInspect, error) {
+	imageRaw, _, err := c.API.ImageInspectWithRaw(c.ctx, image)
+	return imageRaw, err
+}
+
+// IsLocalImage checks if the image has been built locally
+func (c *Client) IsLocalImage(image types.ImageInspect) bool {
+	return len(image.RepoDigests) == 0
+}
+
+// IsDanglingImage returns whether the given image is "dangling" which means
+// that there are no repository references to the given image and it has no
+// child images
+func (c *Client) IsDanglingImage(image types.ImageInspect) bool {
+	return len(image.RepoTags) == 1 && image.RepoTags[0] == "<none>:<none>" && len(image.RepoDigests) == 1 && image.RepoDigests[0] == "<none>@<none>"
 }